Stormwater Network Research Articles

A Low-Cost Water Depth and Electrical Conductivity Sensor for Detecting Inputs into Urban Stormwater Networks.

High-resolution data collection of the urban stormwater network is crucial for future asset management and illicit discharge detection, but often too expensive as sensors and ongoing frequent maintenance works are not affordable. We developed an integrated water depth, electrical conductivity (EC), and temperature sensor that is inexpensive (USD 25), low power, and easily implemented in urban drainage networks. Our low-cost sensor reliably measures the rate-of-change of water level without any re-calibration by comparing with industry-standard instruments such as HACH and HORIBA’s probes. To overcome the observed drift of level sensors, we developed an automated re-calibration approach, which significantly improved its accuracy. For applications like monitoring stormwater drains, such an approach will make higher-resolution sensing feasible from the budget control considerations, since the regular sensor re-calibration will no longer be required. For other applications like monitoring wetlands or wastewater networks, a manual re-calibration every two weeks is required to limit the sensor’s inaccuracies to ±10 mm. Apart from only being used as a calibrator for the level sensor, the conductivity sensor in this study adequately monitored EC between 0 and 10 mS/cm with a 17% relative uncertainty, which is sufficient for stormwater monitoring, especially for real-time detection of poor stormwater quality inputs. Overall, our proposed sensor can be rapidly and densely deployed in the urban drainage network for revolutionised high-density monitoring that cannot be achieved before with high-end loggers and sensors.

Network representation in hydrological modelling on urban catchments in data-scarce contexts: A case study on the Oued Fez catchment (Morocco)

Study regionOued Fez, Morocco. Study focusUrban catchments are heterogeneous in terms of land use and have both natural and artificial drainage networks. Modelling them is not a straightforward task especially in data-scarce settings. This study investigates network representation in hydrological modelling using field data collected between 2008 and 2018 on the Oued Fez catchment. The road network is used as a proxy for the stormwater network. Two production functions, SCS (1972) and a linear reservoir, are coupled to the lag and route transfer function. Three types of land use classes are used. Tests are carried out at hourly and 5-minute time steps using both the natural and modified drainage networks. New hydrological insights for the regionFifty-three rainfall–runoff events are monitored on the urban part of the catchment over the 2008–2018 period. The highest rainfall values are recorded in 2008/2009, while the highest peak flow values are recorded in 2017/2018. This is due to stream channelisation and increased stormwater network coverage. Using the road network with minimal land use classes improves the model performance at both the hourly and 5-minute time steps.

Impact of illegal use of storm network on Tigris River using supervised classification technique

This paper studies the impact of the stormwater network outfall of the Al-Rabee Quarter on the Tigris River. Residents of the district use the storm network for contacts of illegal sewage. Household wastewater is discharged through the storm network directly into the river without treatment, which affects the water quality. Storm network model was developed and use a dynamic wave approach in routing hydraulic flow. The model was simulated based on the calculations of the quantities of domestic wastewater. The supervised classification was used in the spectroscopy of the satellite image of the river by the ArcGIS software in determining the effect of the storm network outfall on the Tigris River. The image was classified into four categories, which are pure water, polluted water, shallow water, and plants. Storm network data was obtained the from Wasit Sewerage Directorate in the form of ArcGIS files. The QuickBird satellite with a high spatial resolution of 25 cm was bought in 2019.The results of the study indicated that sewage quantities were discharged into the river, which led to water pollution by 17.79% from the river surface area. It was concluded from the results that the outfall of the storm network has a high impact on the river water quality. Therefore, this study suggests implementing and managing a separate sewage network that is directed directly to the treatment plants. A stormwater management model (SWMM) was used to simulate a storm network as a sewage network in dry weather.

Evaluating Porous Pavement for the Mitigation of Stormwater Impacts

Urban stormwater management is one of the biggest challenges facing modern cities. The current stormwater networks are likely to be insufficient under continuous urbanisation and the development of residential areas in addition to increases in rainfall intensity, especially in areas with relatively high slopes, which may thus be subject to flooding. This study aimed to mitigate the overflow rate of the selected case study area using a pervious inlets pavement technique based on porous asphalt concrete pavements with a reservoir layer. The current stormwater network system of the Al-Yarmouk quarter (located at the centre of Karbala City, Iraq) was evaluated by exposing it in simulation to a rainfall intensity equivalent to the 5-year return period and applying storm and sanitary analysis (SSA) and GIS software. The simulation results showed that constructing 50% of the road surface area (5% of the total studied area) with porous asphalt concrete with air voids of about 20% and variable reservoir thicknesses, could reduce water runoff entering the network significantly. Moreover, placing 240 mm, 328 mm and 400 mm of No.75 aggregate layer within reservoir depths would result in further mitigations of surface runoff quantity by about 15%, 30%, and 45%, respectively. A reservoir depth of 240 mm was found to reduce flooding quantities and times by about 71% and 18.29%, respectively, while creating a 328 mm reservoir depth under the porous asphalt results in quantity and time reductions of about 98.5% and 81%, respectively. No surface flooding was observed when reservoir depth was changed to 400 mm.

Reducing Flood Risk in Changing Environments: Optimal Location and Sizing of Stormwater Tanks Considering Climate Change

In recent years, there has been an increase in the frequency of urban floods as a result of three determinant factors: the reduction in systems’ capacity due to aging, a changing environment that has resulted in alterations in the hydrological cycle, and the reduction of the permeability of watersheds due to urban growth. Due to this, a question that every urban area must answer is: Are we ready to face these new challenges? The renovation of all the pipes that compose the drainage system is not a feasible solution, and, therefore, the use of new solutions is an increasing trend, leading to a new operational paradigm where water is stored in the system and released at a controlled rate. Hence, technologies, such as stormwater tanks, are being implemented in different cities. This research sought to understand how Climate Change would affect future precipitation, and based on the results, applied two different approaches to determine the optimal location and sizing of storage units, through the application of the Simulated Annealing and Pseudo-Genetic Algorithms. In this process, a strong component of computational modeling was applied in order to allow the optimization algorithms to efficiently reach near-optimal solutions. These approaches were tested in two stormwater networks at Bogotá, Colombia, considering three different rainfall scenarios.

Efficiency of underground retention systems and reduction of urban floods in Tepic, Mexico

Many cities in Mexico experience recurrent floods, caused by changes in land use, the modification of surface and land runoff, the artificialization of areas initially intended for infiltration and recharge of groundwater and, in general, the insufficiency and deficiency of the local networks of urban drainage, incapable to evacuate the annual surpluses of precipitation. In this sense, the objective of this study evaluates the efficiency of an underground system of retention of rainwater in one of the main avenues of the city of Tepic, Mexico: Avenida Tecnologico. To this end, an analysis of the thematic contents and on-site inspection assisted by geographic information systems is carried out. Based on the systems approach and the logic of a qualitative model, it is concluded that the capacity of urban storm water networks for water evacuation is exceeded dimensionally. Also, it can be observed that retention systems can mitigate the urban entropy generated by the floods.

Assessing Redundancy in Stormwater Structures Under Hydraulic Design

As environmental change is happening at an unprecedented pace, a reliable and proper urban drainage design is required to alleviate the negative effects of unexpected extreme rainfall events occurring due to the natural and anthropogenic variations such as climate change and urbanization. Since structure/configuration of a stormwater network plays an imperative role in the design and hydraulic behavior of the system, the goal of this paper is to elaborate upon the significance of possessing redundancy (e.g., alternative flow paths as in loops) under simultaneous hydraulic design in stormwater pipe networks. In this work, an innovative approach based on complex network properties is introduced to systematically and successively reduce the number of loops and, therefore, the level of redundancy, from a given grid-like (street) network. A methodology based on hydrodynamic modelling is utilized to find the optimal design costs for all created structures while satisfying a number of hydraulic design constraints. As a general implication, when structures are subject to extreme precipitation events, the overall capability of looped configurations for discharging runoff more efficiently is higher compared to more branched ones. The reason is due to prevailing (additional) storage volume in the system and existing more alternative water flow paths in looped structures, as opposed to the branched ones in which only unique pathways for discharging peak runoff exist. However, the question arises where to best introduce extra paths in the network? By systematically addressing this question with complex network analysis, the influence of downstream loops was identified to be more significant than that of upstream loops. Findings, additionally, indicated that possessing loop and introducing extra capacity without determining appropriate additional pipes positions in the system (flow direction) can even exacerbate the efficiency of water discharge. Considering a reasonable and cost-effective budget, it would, therefore, be worthwhile to install loop-tree-integrated stormwater collection systems with additional pipes at specific locations, especially downstream, to boost the hydraulic reliability and minimize the damage imposed by the surface flooding upon the metropolitan area.

Regional Flood Forecasting using SWMM for Urban Catchment

Urban flooding is the inundation of land or property in a designed atmosphere, significantly in additional densely inhabited areas, caused by precipitation overwhelming the capability of drain systems, like storm sewers. Due to expeditious increment and improper urban designing the probabilities of creek, localized or flash urban floods have drastically multiplied. This study explores the application of Storm Water Management Model (SWMM) to densely populated area of Vijayawada city, which is fragmented into 58 sub-catchments. The study area is delineated in SWMM by the assistance of blueprint AutoCAD maps showing drainage network and Reference Level details. From this elaborated elevation data of drain networks, the flow direction has been evaluated to create the descriptive view of the area in SWMM. In this study area 2016, 2017 and 2018 extreme rainfall events of 24 hrs interval is considered for runoff analysis. The focus of the current wok is to model runoff conditions by applying Dynamic wave equation for routing floods and Green-Ampt equation for infiltration in SWMM. The model outputs guided in visualizing the runoff from extreme precipitation events and to analyze the accuracy of the storm water network system.

Investigation of The Effect of Climate Change on Stormwater Networks: Capital Ankara Case

Bu çalışmada Ankara İlinin geçmiş dönem ve gelecekteki aşırı yağış ve arazi kullanımı/örtüsü değişim analiz sonuçları, Ankara İli Etimesgut ilçesinde yeni inşa edilen bir pilot çalışma alanının yağmur suyu şebekesi için uygulanmıştır. Sistemin performansı, mevcut ve değişen koşullar ile durağan ve durağan olmayan aşırı yağış varsayımı gibi farklı yaklaşımlar altında araştırılmıştır. Sistemin iklim değişikliği projeksiyonları altında yeterli ve beklenen servisi sağlayabileceği ve aşırı yağış için yapılan iklim değişikliği projeksiyonlarına göre sistemin temel tasarımda öngörülen maksimum kapasiteyi projeksiyon süresi boyunca aşmayacağı söylenebilir. Değişen iklim ve arazi kullanım/örtü koşulları birlikte değerlendirildiğinde sistem, 15 dakikalık yağış süresi ve 2 yıl tekerrür periyodu ile akış katsayısı olarak 0,8 kullanılan temel tasarım için tatmin edici bir performans ortaya koymaktadır. Öte yandan sistem gözlem verisi ile yapılan durağan ve durağan olmayan analizlerden elde edilen daha uzun yağış süreleri (30 dakika veya daha fazla gibi) veya daha yüksek tekerrür süreleri (5 yıl ve daha fazlası gibi) ile ayrı ayrı veya birlikte hesaplanan yükler altında beklenen servisi sağlayamayabilir ki bu süreler kritik bir altyapı tesisi ve alan için tercih edilen bir tasarım girdisidir.

Hydraulic calculations of storm sewer networks

Surface run-off (SR) produced on the territory of cities and other settlement as a result of atmospheric precipitation is an intensive source of the technogenic pollution of environment, including the waterbodies. In accordance with the existing legislation of the Russian Federation, SR requires organized disposal and treatment according to the standards of regulatory documents. In this article we analyze the European document BS EN 752:2017 with regard to determining the flow-rates of surface (storm-water) run-off, and the calculations are made by the authors, which demonstrate that the application of foreign software products is impossible in Russia, due to the differences between the existing Russian regulatory and methodological documents and the European standards. Nevertheless, for the development of electronic models of hydraulic calculations for a storm-water drainage network, the mathematical relationship, which most adequately characterizes the type of surface run-off hydrograph most frequent for the territory of the Russian Federation as a result of atmospheric precipitation, was found. The relevant algorithm of the hydraulic calculation of storm-water drainage networks was also developed.

Hydrological Functioning of an Evolving Urban Stormwater Network

AbstractAs complex systems, urban stormwater networks (USNs) may reveal emergent features (e.g., scaling) and sudden changes in behavior, which can lead to unanticipated impacts. We explored this through the USN properties of connectivity, heterogeneity, and scaling, which were quantified using outputs from a hydrological model and network dispersion mechanisms. The network properties were determined retrospectively in space and time by reconstructing the contemporary history of urban development and stormwater infrastructure in an arid, urban catchment in the City of Scottsdale, Arizona, USA. We found that the relative importance to USN functioning of both network structure (geomorphology) and dynamics (spatial celerity pattern) changed with the spatial scale, with network geomorphology being more dominant at larger spatial scales. The importance of network geomorphology suggested that the structure of the USN itself could potentially serve as a stormwater control measure, for example, by enhancing flow dispersion. The temporal evolution of the USN revealed a sudden change in the hydrological functioning of the network, which seemed to be a consequence of the combined effects of patchy urban development and changes in network connectivity. The interactions between the urban spatial pattern, stormwater infrastructure, and surface runoff may result in threshold‐like behavior. A spatial multiscale approach to stormwater management may be beneficial to ensure that hydrological benefits at one scale do not cause unintended consequences at another. Overall, the retrospective modeling and network analysis approach used in this study may be useful for understanding emergent urban stormwater impacts.

A suburban sediment budget: Coarse‐grained sediment flux through hillslopes, stormwater systems and streams

AbstractSediment in urban stormwater systems creates a significant maintenance burden, while a lack of coarse‐grained bed sediment in streams limits their ecological value and geomorphic resilience. Gravel substrates, for example, provide benthic habitat yet are often scoured from the channel bed only to end up in a detention basin or treatment wetland. This dual problem of both ‘too much’ and ‘too little’ coarse‐grained sediment reflects a watershed sediment budget that is profoundly altered. We developed a conceptual urban coarse‐grained (>0.5 mm) sediment budget across three domains: hillslopes (urban land surfaces), the built stormwater network and stream channels. We then quantified key sources, sinks and storages for a suburban case study, using a combination of hillslope and in‐channel monitoring, and interrogation of local government records. Around 36% of the sediment supplied to the stormwater network reached the catchment outlet, a level of sediment delivery much higher than observed in similar‐sized natural catchments. The remainder was deposited in the sediment cascade and either stored, or extracted and removed from the catchment (e.g. material deposited in sediment ponds and gross pollutant traps). Conventional urban drainage networks are characterized by high hillslope sediment supply and low storage, resulting in efficient sediment delivery. Channel erosion, deposition in (and extraction from) pipes and channels, and floodplain deposition are small compared to sediment transport through the cascade. An understanding of the sediment budget of urban headwater catchments can provide stormwater and waterway managers with the information they need to address specific sediment problems such as sedimentation in stormwater assets and geomorphic recovery of urban streams. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.

Trenchless Limitations on Postearthquake Repair and Rehabilitation of Unpressurized Networks: Christchurch, New Zealand

AbstractEarthquakes are one of the most devastating natural disasters, annually causing severe damage to underground infrastructures, including unpressurized wastewater and stormwater networks. Aft...

Using spatially-identified effective impervious area to target green infrastructure retrofits: A modeling study in Knoxville, TN

There is a need for enhanced guidance in siting distributed, infiltrative green infrastructure (GI) practices, especially in densely developed urban watersheds where retrofits come at a high cost. To maximize the hydrologic benefit of GI practices on urban streams, the disconnection of effective impervious areas (EIA), or those impervious areas hydraulically connected to the stormwater network, has been identified as a strategic management approach that is expected to have the greatest impact. The overall effect of full disconnection of spatially-identified EIA on watershed hydrology is uncertain because this type of full disconnection is rarely brought to full-scale implementation. In this study, spatial EIA identification is used to parametrize an urban runoff model using the United States Environmental Protection Agency’s Storm Water Management Model (SWMM). The calibrated model is used to assess runoff reductions resulting from GI practices distributed through the watershed via different placement strategies, both spatially-informed and not. Full treatment of the spatially-identified EIA using bioretention cells was compared to two scenarios treating the same area of impervious surfaces, but with random placement either among all impervious areas or placement focused in areas of higher imperviousness. Model results indicate that substantially higher runoff reduction could be realized by targeting EIA, with a median runoff reduction of nearly 30% more than other treatment scenarios across storm events ranging from 1.27 to 20.7 mm using this strategic siting. Further improvements in optimizing distributed infiltrative GI practice placement are needed and targeting of spatially-identified EIA appears to be a viable method for increasing the hydrologic improvements realized through watershed scale implementations.

Peak Flows and Stormwater Networks Design—Current and Future Management of Urban Surface Watersheds

Stormwater urban drainage systems are typically designed in open channel flow. Pipe sewers must have enough capacity to transport maximum design flows for a given frequency of the project rainfall. The classic rational method or related procedures that are based on rational approaches are still currently used to a great extent, particularly for small urban drainage basins, and the pipes are frequently designed in uniform steady flow. Numerical integration of Saint-Venant equations for one-dimensional gradually varied unsteady flow allows the computation of waves’ progression along the pipes for given input surface hydrographs. This paper presents a comprehensive, systematic, simple, and original comparison between the peak flows that are achieved through simulation in unsteady flow using an implicit complete dynamic model, developed in the Laboratory of Hydraulics, Water Resources and Environment of Coimbra University, and those that are obtained with the classic rational method along urban drainage networks. Boundary conditions and some approximations typically considered in the methodologies are analyzed in detail. Classic rational approaches may underestimate the peak and design flows. Practical recommendations for the system design phase when rational approaches are used are also proposed. The need for indispensable requirements for suitable urbanization rules, intelligent management of surface runoff in urban basins, and control measures for the reduction of peak flows entering existing networks is confirmed and reinforced.

Modelling the impact of design rainfall on the urban drainage system by Storm Water Management Model

Abstract Flood modelling is an effective way to manage the stormwater network in cities. It aims to understand and predict the behaviour of stormwater network so that it can test and evaluate effective solutions to structural and operational problems. So simulation modelling stays a preoccupation for building a successful hydraulic modelling in urban areas. This study investigates the impact of the design rainfall on the hydraulic modelling results for the Azzaba stormwater network located in the North-East of Algeria by using the Storm Water Management Model (SWMM). Four scenarios of design rainfall events were compared for 10, 25 and 50-year return periods, where we used double triangle and composite curves for the design rainfall event definition. The results show the impact of the choice of design rainfall on the behaviour of the stormwater network, from which the results of simulation by the double triangle method for the short durations represents a great risk on the probability that the stromwater network can overflow and flood the city, with a difference in peak discharge estimated at 62.97% and 58.94% for 2 h and 3 h events compared to the peak discharge simulated by the composite rainfall method.

Groundwater recharge in urban areas (Porto, NW Portugal): the role of GIS hydrogeology mapping

A delineation of groundwater potential zones was performed and an urban infiltration potential index (IPI-Urban) was proposed. The pilot site was the Paranhos and Salgueiros water galleries and surroundings in Porto City (NW Portugal). An integrated approach combining hydrogeomorphology and GIS was developed applying multiple layers of information (tectonic lineaments, hydrogeotechnical units, slope, drainage, land use, sewage and stormwater networks, water supply system and rainfall). Different ranks were assigned to thematic layers and classes received different weights according to their contribution to define groundwater potential areas using the AHP methodology. Two scenarios, Summer and Winter, were computed. 81% of the region is covered by urban and industrial areas and streets. Three areas were identified for major potential direct groundwater recharge (SE of Arca d´Agua site, E-SE of Burgaes site and W-NW of Lapa site). A Moderate to Low IPI-Urban prevails, and the High and Very high IPI-Urban appear mainly along the three cited valleys. A low to very low recharge was estimated, with less than 50 mm/year and 6% on the Winter scenario. Aquifer potential yields in the Winter scenario are in the range of 1–2 L/s/km2. The IPI-Urban is a valuable tool for integrated water resources management in urban areas.

Assessing the Water Energy Nexus and Sustainability Benefits of a Closed Loop Water Treatment System in Qatar

Qatar has very limited freshwater resources. This paper assesses the sustainability implications of using bore water and treated sewage effluent (TSE) for residential water supply (for non-drinking purposes) in a residential compound in Doha, Qatar. The treated bore water was considered for non-drinking domestic applications in kitchens and bathrooms, while the TSE was considered for use in air conditioning cooling systems. Excess TSE was also considered for irrigation use. Water quality from the aquifer in the Al Waab area of Doha was used to design a pre-treatment and desalination process to produce potable water for a local residential compound consisting of 113 villas. The wastewater from these villas consisted of both grey and black water and was proposed to be treated in a sewage treatment plant to produce TSE to operate the cooling systems in the compound. The reject brine from the desalination process was designed to be discharged to sea through the storm water network and the blowdown water from the cooling systems was considered for use in irrigation in surrounding areas. A lifecycle assessment of this closed loop water recycling system was conducted to assess the potential sustainability benefits of reduced greenhouse gas emissions, embodied energy consumption, and water consumption, together with cost savings and employment generation from these water recycling options.

A Semi-Automatic Approach in GIS for 3D Modeling and Visualization of Utility Networks: Application for Sewer & Stormwater networks

This paper presents a semi-automatic methodology proposed for 3D modeling of utility networks in GIS environment. The ModelBuilder in ArcGIS (ESRI) software is used for implementing this methodology, by developing two tools to automate the construction processes of 3D networks. The first presents a tool to create a 3D Manhole layer from points layer, and the second is a tool to create a 3D pipe layer. For both tools, a work algorithm has been built, in addition to designing user interfaces elements. These tools are stored in a Toolbox called “3D Manhole & Pipe.tbx”. The two previous tools were tested and applied to spatial data for a proposed residential area. The final 3D model of the residential area includes the sewage and stormwater networks, as well as other spatial data such as buildings, parks, roads, etc. This model is able to spot the intersection points in the network, visually or using the 3D analysis available in the software, allowing us to identify problems to be processed and resolved before starting a project, leading consequently to time and cost savings, effort and money. The proposed methodology is an easy and an effective way to build 3D network models (sewer, water..etc), and the developed tools allow the implementation of a set of necessary processes needed to build 3D networks.

Urban floods in Hyderabad, India, under present and future rainfall scenarios: a case study

This study assesses and evaluates the impacts of future extreme rainfall event(s) on conveyance capacity of urban Storm Water Network (SWN) of Hyderabad City, India, along with flood risk analysis and inundation mapping. The catchment runoff volume was simulated using Storm Water Management Model (SWMM). The runoff simulations were carried out for historic and future extreme rainfall event(s). Future rainfall events were simulated under climate change scenarios using Global Climate Model (GCM), GFDL-CM3 of Coupled Model Intercomparison Project Phase 5 (CMIP5). Nonlinear regression-based statistical downscaling was used to obtain rainfall at regional scale for Representative Concentration Pathways (RCPs) 2.6, 4.5, 6.0 and 8.5. It was found that RCPs 2.6, 4.5, 6.0 and 8.5 predicted a future extreme rainfall of 693 mm, 431 mm, 282 mm and 564 mm for the years 2088, 2098, 2040 and 2068, respectively. SWMM results indicated that the future extreme rainfall in Hyderabad can result in increased runoff volumes causing flooding. The existing SWN was capable of handling RCP 6.0 with 82% runoff. However, it was inadequate to convey runoff from RCPs 2.6, 4.5 and 8.5. Modelling results suggest that the conveyance capacity of storm drains can be increased by 25–30% by desilting major drains and outlets.